This invention relates to building insulation and more particularly to such insulation for use particularly in floors above crawl spaces, garages and basements of heated buildings.
It is common practice to insulate buildings with batts of fibrous insulating material, such as glass wool and the like, to which a vapor barrier layer is applied on one side thereof, as is well known. Proper installation of these batts requires that they be installed with the vapor barrier layer facing the heated area, i.e., the inside of the building structure.
The vapor barrier layer of these batts is provided with fastening lips or flanges in the form of elongated extended edge portions running along the length of the batts on the opposite sides thereof. When it is desired to install the batts in the walls of buildings it is merely necessary to insert them in place between the wall studs and secure the flanges to the studs by nails or building staples. This is a very simple and quick operation to accomplish since the vapor barrier layer is installed away from the outer wall of the building. i.e., closest to the inner wall to be installed over the insulation batt.
The use of such batts for insulating the floor over a crawl space or basement, however, presents several difficulties. Since the vapor barrier layer should be installed facing upward, it is extremely difficult to nail or staple the fastening flanges thereof to the overhead floor joists because the insulating material fills the space between the joists. Accordingly, it has become a not-uncommon practice by workmen to install the batts so the vapor barrier layer thereof faces downward so they can quickly and easily staple the fastener flanges to the floor joists. This, of course, places the vapor barrier layer in the improper position, whereby it "encloses" the insulating material of the batt between the barrier layer and the inside atmosphere of the building. This results eventually in the formation of condensation in the insulating material, thus substantially reducing its effectiveness as a heat insulator.